Low boron ferrotitanium alloy



Ernest HJ Wyelie, Lewiston, N Y., 'assignor to Union Carbide Corporation, a corporation of New York No Drawing. Application September 5, 1956 Serial No. 608,006

4 Claims. c1. 75 -1755 This invention relates to a low-boron, high-titanium master alloy. I I The present invention is based on the discovery that suitable additions of boron greatly improve the stress-rupture properties of high temperature steels and. alloys. At least about one or two parts boron per million is required to secure substantial benefits, and in some cases more than about fifty parts boron per million destroys the workability and other mechanical properties of the steel. The most desirable boron content in respect to one type of alloy has been found to be between about two and fifty parts per million.

The present practice of adding such minute additions of boron to high temperature alloys in the form of alloys of boron and iron is not altogether reliable. Being quite small, the boron addition requires very careful weighing. If insuflicient boron is added, poor stress-rupture values result, while if excessive boron is added, hot-shortness and other mechanical properties are adversely affected. Conventional high-boron alloys containing 16% to 18% boron are not amenable to control as the very small amounts are ditlicult to accurately weigh under the usual operating conditions. In addition, there is no assurance of the boron diffusing uniformly through the bath to give a homogeneous composition. Low-boron iron base master alloys containing about 1.5% to 2.5% are normally satisfactory additions in most respects; however, most of these alloys do not possess suificient universality to enable them to be satisfactorily used for critically controlling the boron content in a melt to a narrow, limited range on the order of between 2 and 50 parts per million.

It is, therefore, an important object of the present invention to provide an improved boron-containing master alloy for controllably adding small quantities of boron to a melt.

Another object is to provide an improved low-boron titanium master alloy for controllably incorporating small quantities of boron in a melt along with the addition of titanium.

Another object is to provide means for imparting to high temperature steels and alloys, an improved resistance to metal sensitivity and better elongation without imparting hot shortness.

. According to the present invention, the high temperature properties of steels and other alloys may be considerably enhanced by the introduction of a titanium master alloy containing relatively small amounts of boron. I have discovered that by formulating the alloy with a fractional percentage of boron up to about 0.5% by weight, along with higher titanium contents above about 61 by weight, the formation of high temperature steels having improved stress-rupture properties at high temperatures may be more controllably produced. Low-boron, high-titanium master alloys according to the invention contain about 0.005% to 0.5% boron, 61% to 90% titanium and the remainder iron and incidental impurities. The preferred master alloy composition of the invention to be used in the Patent "aluminum; 1 0.04%

. load: oi3;aproxiinatelyu62,500l p: is

" following table' of data for typical stress-rupture tests obtained on fully annealed, boron-enriched;titaniumcontaining. steel-:Fbarsr. A'-"typicalranalysiswdf the lowboron, high-titanium .ainaster alloyremployed in forming thesesteeltbar's is"66.66%t titanium; 27.39% iron, 3.64%

"1' t p0.04%-.copper, 0.01% phosphorus; 0.06%721."v rcarbon, .0113 .'-nitrog'en; t 0.31% chromium, 0.04 molybdenum, 0.60%.. oxygen, 0.014% hydrogen, 0.011% 5su'lfur;:- 0.06%* -boron,'*and 0.30% manganese: The stresswrupturedes'tsi were co'nducted on smoothand notched bars eati 1200" Funder. atensile stress lit ill accordance with the practices and technical requirements 6.1, 6.3, 6.4, 6.4.1, and 6.4.2 outlined in Aeronautical Materials Specification 5735.

STRESS RUPTURE TESTS Analyszs Average Average Number Percent Tl, B, Fe and of Hours Elonga- Peroent Percent Incidental Duration tion Impurities to Rupture (Smooth (Notched Bars) Bars) Steel A l 1.83 0. 0001 Balance. 46. 8 2. 5 Steel 13 1 1. 89 0.0007 Balance 304. 8 9. 7

1 Typical compositions of the test bars are as follows:

Steel A Steel 13 0 001 0.003 0. 004 0. 009 B 0. 0001 0. 0007 Fe and Incidental Impurities Balance Balance From the above data it will be seen that when small amounts of boron are introduced into steels in the form of a low-boron titanium alloy, there is obtained a six-fold improvement in stress-rupture life, as measured by standard notched bar tests. The average elongation values (9.7% of smooth metal bars treated by the subject master alloy exceeds by nearly four-fold the elongation values for smooth bars having approximately the same base compositions, but less than 0.0001 boron.

One of the important advantages of the master alloy of the invention is that it permits the introduction of the desired titanium and boron values into a melt in a single addition with improved control.

The characteristics of the subject master alloy result in a more rapid rate of solution when added to a molten bath than is obtained with similar alloys containing less titanium.

A typical low-boron, high-titanium alloy of the invention may be made by melting proper proportions of iron and aluminum in an electrically energized furnace and adding suitable quantities of titanium and ferroboron through an inert atmosphere. Following are the mix order of the ingredients employed in the manufacture of a boron enriched ferrotitanium alloy according to the principles of the invention, and an analysis of the result- While I have shown a single embodiment of my invention, it will be understood that this embodiment is merely for the purpose of illustration and description, and that various other forms may be devised within the scope of my invention as defined in the appended claims.

What is claimed is:

1. A ternary master alloy consisting of boron, titanium, iron and incidental impurities, the boron constituting up to 0.5% of the alloy, the titanium at least 61% of the alloy, and the remainder iron and incidental impurities.

2. An alloy composition especially adapted for improving the stress-rupture and elongation properties of a high temperature steel, said composition consisting of about 0.005% to 0.500% boron, 61% to 90% titanium and the remainder iron and incidental impurities.

3. An alloy consisting essentially of 0.005 to 0.500% bor-on, 61% to 90% titanium and the remainder iron and incidental impurities.

4. An alloy consisting of 0.01% to 0.20% boron, 61% to 80% titanium and the remainder iron and incidental impurities.

References Cited in the file of this patent UNITED STATES PATENTS Jafiee et a1. May 13, 1952 OTHER REFERENCES Titanium Project, Navy Contract No. Noa( s) 9919. Report 7, PB 100,000, July 14, 1950. Pages 15, 16, 46, 48 through 51., 

1. A TERNARY MASTER ALLOY CONSISTING OF BORON, TITANIUM, IRON AND INCIDENTAL IMPURITIES, THE BORON CONSTITUTING UP TO 0.5% OF THE ALLOY, THE TITANTIUM AT LEAST 61% OF THE ALLOY, AND THE REMAINDER IRON AND INCIDENTAL IMPURITIES. 